Recommendation ITU-T Y.2812 describes the
mobility management framework for interworking between WiMAX and UMTS
networks. The mobility management framework in this Recommendation focuses on
vertical handover control in the transport stratum of next generation networks
(NGNs) when a user equipment with multiple interfaces moves across those two different
wireless access networks. The requirements, functional architecture and
procedural information flows are given to specify the vertical handover
control functionality.